I have a friend on a multiple entry Non-immigrant O Visa, it expires on May 13. If he does a border run on May 08, will he get another 90 stay in the Kingdom before he has to apply for a new visa?
TLDR : Answer Summary
If your friend performs a border run on May 8, just before his Non-Immigrant O Visa expires on May 13, he should receive another 90 days of stay in Thailand as long as he re-enters before the expiration date mentioned on the visa.