1. It appears you are an Indian. You can either buy a 60 day tourist visa while in India, or get a 15 day Visa on Arrival. It sounds like you are planning on getting a Visa on Arrival.
2. You can purchase a re-entry permit to keep your visa active. It should be 1,000 THB. You can get that at the immigration office, or the airport.
3. I believe you are able to get as many VOAs, however, you will have to show your ticket out of Thailand, and the triple proofs (source:
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