Analysts say Thailand urgently needs to implement policies that address the declining population in the same way that Singapore has done in recent years.
Singapore also faces an aging population and low birth rate but has worked to offset this in recent years through steps such as ramping up migration. Those policies mean Singapore's population is expected to peak later than its regional peers.
(Read more: Singapore: A Wealthy Nation That Can't Afford to Retire)
In August, the Thai National Economic and Social Development Board urged the government to draw up a family-development plan to cater for a highly dependent population after 2040 and to promote sufficient retirement savings, local newspaper 'The Nation' reported.
It says that by 2040, a quarter of the Thai population could be over the age of 65.
"I'm sure we can do better," said Supavud Saicheua, head of research at Thailand's Phatra Securities, talking about measures taken to support an aging population.
"There is now universal healthcare and benefits are being expanded from a social security system set up several decades ago," he said. "Industrial workers and civil servants have pension funds. But over 20 million workers in the agricultural and informal services sectors do not have such schemes and it is likely that they will not have enough savings to retire on."
(Read more: Are Asia retirees missing out on a key savings tool?)
Rotjana Patikarapong, who left Thailand five years ago and lives in Singapore with her family, says she would not consider returning home to retire.
"We don't have a system like the CPF in Singapore and there doesn't seem to be a policy about caring for the elderly," she said, referring to Singapore's Central Provident Fund – a compulsory savings scheme that citizens can use for retirement, housing or healthcare.
Analysts say one option for Thailand to address the aging population quickly is to encourage more migration. Reforming the education system to produce a more productive labor force is another area the government should look at more closely, they add.
"There is a lot of room to increase labor productivity – reform of education to produce the right manpower is something that is long overdue," said Phatra Securities' Saicheua.
Whatever the government does it needs to do quickly, added HSBC's Lim.
"The longer you leave it the harder the problem of addressing an aging population becomes," she says. "And Thailand has left it very late."
—By CNBC.Com's Dhara Ranasinghe; Follow her on Twitter @DharaCNBC