Indan Citizens need to get a transit visa. You can get a visa at an embassy or consulate before you travel or get a visa on arrival.
Visa can be obtained on arrival (ONLY at Bangkok, Chiang Mai,
Chiang Rai, Hat Yai, Phuket, Samui Int'l, Sukhothai, Surat
Thani, Utapao airports) for a stay of max. 15 days, provided:
- coming for touristic purposes; AND
- passport is valid at least 6 months; AND
- holding onward/return ticket; AND
- holding USD 250.- per person or USD 500.- per family.
More info here
http://www.thaiemb.org.in/visa/typeofvisa.asp#Transit