Financial institutions can readily begin lending under the nanofinance programme while non-banks can apply to become operators with the Finance Ministry.
The central bank's notifications governing the business took effect on Saturday.
Under the announcements, nanofinance is defined as lending not more than 100,000 baht per person with no collateral to help people start businesses. The effective rate - interest rate, fines and all fees - must not exceed 36% a year.
Fourteen companies, most of which are non-banks, have applied to become the small lenders, Ronadol Numnonda, assistant governor for supervision of the Bank of Thailand, said on Tuesday.
"If their documents are ready, the central bank can forward their applications to the Finance Ministry immediately and they can start lending within 60 days.
"We'll know the exact number [of applicants] over the next 2-3 weeks," he said.
The loans aim to deter loan sharks. According to a central bank survey, 600,000 out of 20 million households borrowed from loan sharks, who charge more than 30% a month, leaving them perennially indebted. It also found some 1.3 million households could not access financial services in the system.
A nanofinance lender must have paid-up capital of at least 50 million baht and a debt-to-equity ratio of no more than seven times. If the ratio exceeds the required level, it needs to bring it down to comply by Jan 23, 2016.