Should I obtain a re-entry permit for my Non-Immigrant B visa before traveling to the Philippines and returning to Thailand?

My husband and I are here working in a government school on Non-Immigrant B visas that are valid through April 30th. The normal school year is finished, however we are teaching an extra class through the end of this week. Next week, March 18th, we are flying to the Philippines and returning to Bangkok on March 31st. We are staying in Thailand and then we will be flying home to the U.S. on April 23rd. My question is, should we get a re-entry permit since our visa is still active through April 30th, or should we leave and come back to Thailand on a tourist visa and show our proof of a return flight to the U.S.?