Indians who get visa on arrival are given a 14-day visa.
The visitors entering on the 60-day tourist visa are still eligible for the extra stay of 30 days.
The move which would come into effect from tomorrow is designed to boost tourism, said Voravat Amornvivat, deputy commander of the bureau's Investigation Division.
The measure will appeal to foreign travellers who want to prolong their stay in Thailand and visit other Southeast Asian countries, Vorarat said.
The extension will cost around Rs 4,000. The bureau, however, tightened up visa extension regulations for foreigners who enrol to study Thai language in private schools outside the official school system as well as those working in a non-profit organisation or foreign chamber of commerce.