Entrance to the temple is free for all.
Due to the disrespectful behaviour of some foreign tourists, Wat Rong Khun has recently instituted a policy requiring guides for foreign tourists visiting the the main temple building. The policy however is not always enforced. Should you wish to have a guide or be required to hire one, there are a number available at the temple itself. The fee for a guided tour with a knowledgeable guide is in the several-hundred baht range. If you do enter without a guide, please do act respectfully and refrain from taking photos inside.