In two weeks, Prime Minister Lee Hsien Loong and other South-east Asian leaders will be in New Delhi to mark the silver jubilee of Asean's partnership with India.

Last weekend, Singapore caught a glimpse of the promising Asean-India chemistry when some 4,000 people with an India connection gathered to explore how the age-old ties could be extended.

India-Asean affinities - strategic, cultural or philosophical - have long been strong. The tide may now be turning with economic ties. The India story has become more compelling, with its economy accelerating just as China slows down.

At the two-day India diaspora conference at Marina Bay Sands, Indian Foreign Minister Sushma Swaraj and Transport Minister Nitin Gadkari spoke of milestone reforms, the billion-dollar infrastructure push and the newfound ease of doing business.

DBS Bank chief Piyush Gupta saw value for Asean in India-made financial innovation, and tantalised the gathering by asking if the Singapore Exchange could be a financial hub for India the way London is for the Middle East.

The mood could even be described as ebullient, but it has to be remembered that this promise has been belied before, the potential never fully realised. Trade between Asean and India has grown twentyfold over the past 25 years to US$58 billion (S$77 billion) in 2016, but well short of the US$100 billion target set for 2015. Trade with India accounts for less than 3 per cent of Asean's external trade.

While India retains the title of the world's fastest-growing economy, there is disquiet about growth, which may hit a four-year low of 6.5 per cent for the year ending March.

The biggest question surrounds the Regional Comprehensive Economic Partnership (RCEP). India has misgivings over what the RCEP might mean for its services sector and could well choose to duck the historic opportunity to be part of the world's largest trade bloc. That would be a pity.