Mr Reagan ran for office from the right but he governed from the centre. He appointed strong, competent and experienced men and women to serve in his administration. He empowered them and did not try to micromanage them.

In the same way, my hope is that you will recruit some of the most qualified, competent and experienced men and women, within and without the Republican Party, to serve in your administration. The Republican Party has a deep talent pool. Since you are an iconoclast, you should also consider appointing some outstanding politically independent individuals to join your team.

ELECTION RHETORIC IS NOT POLICY

My second piece of advice is to disregard your election rhetoric in the making of policy. In the course of the long campaign, you made remarks that resonated with the audience or your constituency but which would make bad policy. You should avoid the trap of being held accountable for those remarks. You need not have a bad conscience about it because every US president before you did the same thing. You are just following a well-known US tradition.

US-JAPAN RELATIONS

The country in Asia that needs your reassurance the most is Japan. The Japanese are nervous about your attitude towards the US-Japan security alliance. They are worried about the reliability of the US nuclear umbrella. The trust of the Japanese government and people in the US is at stake.

This is happening at a time of rising nationalism in Japan. A new generation of Japanese leaders are beginning to express the view that the time has come for Japan to transcend the US-inspired peace Constitution and to amend Article 9 of the Constitution.

This process will be accelerated if the trust of the Japanese people in the reliability of the US security guarantee is undermined. If Japan becomes a "normal" country and decides to acquire nuclear weapons, this will set in train developments in North-east Asia, which could destabilise the whole region.

It is therefore important for you to reassure your Japanese ally of your commitment to the US-Japan security alliance. This alliance is important not only to the two contracting parties, but also to the peace and security of the entire Asia-Pacific region.

US-CHINA RELATIONS

Another country in Asia that needs your urgent attention is China. In the course of the campaign, you said some unkind things about China. You threatened to withdraw from the World Trade Organisation (WTO) and impose tariffs on Chinese exports to the US.

As a friend of both the US and China, I would like to say that you should not regard China as an enemy of the US. The truth is that you are dependent on each other.

China is your biggest creditor country and the US is China's largest export market. Beyond economics, you have congruent interests in nuclear non-proliferation, climate change, the Korean peninsula, Iran, terrorism and other issues.

For over 40 years, every US administration since the Nixon administration has pursued a bipartisan policy towards China. The policy is to engage China and to persuade it to be a responsible stakeholder. The policy is to cooperate with China where your interests converge, to compete where they diverge and to manage your differences on the basis of mutual respect and mutual benefit. It would be good if you could affirm your support for this policy.

There are many in Asia who worry that the US and China may fall into the Thucydides Trap. We do not want a hot or cold war between the incumbent hegemon and the challenger.

On the question of your trade policy, many in Asia are extremely nervous about your protectionist election rhetoric. We understand that one of your constituencies consists of workers who have lost their jobs because of the closure of their industries or companies. Many of them have remained unemployed for many years. Their towns and villages have been devastated by such closures. They have become victims of a vicious circle. You have promised to bring their jobs back and to prevent US companies from relocating their manufacturing operations overseas.

As a good businessman, you know that competition is a fact of life and protectionism is a dead-end road.

You know that technology and the relentless logic of comparative advantage will force some industries and some manufacturers to relocate in order to survive.

Instead of trying to protect jobs in such sunset industries, you should focus on promoting jobs in sunrise industries. Instead of erecting walls against foreign competition, you should focus on incentivising sunrise industries to locate in these depressed areas of your country, to reskill the workers who have been laid off and to provide a cushion to support them in the transition.

America's future is in the sunrise industries and not in the sunset industries. The truth is that, on the whole, free trade and globalisation are forces for good and not evil.

As a businessman, you know how important it is for the business environment to be stable, transparent and rules-based. What is true of the domestic economy is also true of the world economy. We need a stable, transparent and rules-based international economic order. The WTO provides such an order for international trade. The WTO serves US national interests.

US-ASEAN RELATIONS

Of all the sub-regions of Asia, the one sub-region that is the most peaceful, prosperous and friendly to the US is South-east Asia.

The sub-region has a population of over 600 million, hosts more US investment than China, Japan and India put together, is blessed with abundant natural resources and sits astride some of world's most important sea lanes. The sub-region also has a world-class regional organisation, Asean.

Since 2009, except for 2013, the US president has held an annual summit meeting with the 10 leaders of Asean. The US president has conscientiously attended the annual meeting of the East Asia Summit.

It would be very good if you could reaffirm the US commitment to Asean and make every effort to attend the two summits. It would also be greatly appreciated by this region if the Trump administration could reaffirm the US support for Asean unity and neutrality, as well as the central role it plays in the regional architecture.

I join the many friends of America in Asia in saying that we would very much like to see you succeed as president. Good luck.

Yours respectfully, Tommy Koh.

• The writer served as Singapore's Ambassador to the US from 1984 to 1990. He is currently co-chair of the China-Singapore Forum and the Japan-Singapore Symposium.