@Deepak ******
Well I might have poor understanding, I am very sorry mr, know everything better, I base my info on the website of the official Thai embassy:
4. Recommendations for foreigners with Non-Immigrant Visa “O-A” (Long Stay) while staying in Thailand
4.1 Upon arrival, holder of this type of visa will be permitted to stay in Thailand for 1 year from the date of first entry.
4.2 At the end of the 90-day stay, the foreigner must report to the immigration officer in his or her residence area and report again every 90 days during his or her stay in Thailand. The foreigner may report to the police station if there is no immigration office in his or her residence area.
4.3 Foreigner may report to the competent authority by post and should provide the following:
A report form (Tor Mor 47)
A copy of passport pages showing the foreigner’s photo, personal details, and the latest arrival visa stamp
A copy of the previous receipt of acknowledgement
A self-addressed envelope with postage affixed.
Such documents must be sent to the Immigration Division 1, 120 Moo 3, Government Center B, Chaengwattana Soi 7, Laksi, Bangkok
*****
and must be submitted 7 days before the end of every 90-day period. A receipt of acknowledgement will be given and should be used for future correspondence.
4.4 Foreigner who wishes to extend his or her stay can contact the Office of the Immigration Bureau directly. A one-year extension of stay shall be granted at the discretion of the immigration officer.