The National Savings Fund (NSF) received a good response from self-employed workers on its first day, with close to 154,000 applying for membership.
Secretary-general Somporn Chitphentom said 153,835 informal workers registered on Thursday, paying in 137 million baht.
The membership ranks are expected to reach 600,000 this year, 1.5 million next year and 3 million by 2018, he said.
Nearly 25 million informal workers who are not covered by the Social Security Fund, the Government Pension Fund or provident funds — including farmers, housewives, freelancers, street vendors, doctors, politicians and taxi drivers aged 15-60 — are eligible for the retirement safety net provided by the NSF.
The minimum monthly contribution is 50 baht up to a maximum per year of 13,200 baht.
The amount is matched in full or in part by the government up to a prescribed limit.
The government will contribute up to 50% of savings but not more than 600 baht a year for workers aged 15-30, up to 80% but not more than 960 baht a year for workers aged 31-50 and up to 100% but not more than 1,200 baht a year for those over 50.
The government's contribution will be adjusted every five years in line with the economic circumstances at the time.
A retirement safety net has become vital as Thailand turns into an ageing society.
By 2020, the number of Thais aged 60 or over is forecast to rise to 10.5 million or 15% of the population, up from 4 million now.