SINGAPORE (Reuters) - Singapore's mid-tier property developers are laying the first stones of their overseas business as domestic sales plunge, land prices climb, and foreign rivals bet high stakes on the city-state's long-term prosperity.

Hiap Hoe and Oxley Holdings followed sector leader CapitaLand this year by going abroad. At home, government action to slow the rise of record-high prices led to a 50 per cent drop in third-quarter private home sales.

Official plans for a significant supply of new homes over the next decade make the price outlook even dimmer. Yet land prices have rallied, pushed up by foreign developers drawn by political and economic stability.

"The Singapore market is now very tough," said Teo Ho Beng, Hiap Hoe's chief executive officer. "Getting new land is a challenge, because there is so much competition."

Hiap Hoe made its first foray abroad by buying three properties in Australia in the past four months. In coming years, most of its revenue will likely come from outside the island-state, Teo said.

Oxley Holdings bought property and invested in developers in Britain, Cambodia, China and Malaysia. Sim Lian Group added to its overseas portfolio by buying property in Australia.

SingHaiyi Group, which earns 98 per cent of revenue in Singapore, bought two properties in the United States this year and appointed Neil Bush, brother of former US President George W. Bush, as non-executive chairman. The company shifted focus to Singapore two years ago in response to property-price cooling measures in its native Hong Kong.