Cognomen Monruethai (มลฤทัย 
, มนฤทัย , Monruethai ) , worldwide, is a very rare family name. The last name Monruethai is habitual in South-eastern Asia, particularly Thailand, where it is a very rare surname. Much more prevalently, Monruethai is the forename as well as the last name.
Imam, Khoonsuk, Klaibood, Jeenawong, Thonglue, Templong, Sueksakan, Chaiwiset, Khaophong, Armatmontri, Chanphakdee, Chaijaroen, Phuttharak, Narongchai, Ratthanarangsi, Fungmongkonsathian, Kaeochure, Kaeochuea, Bunpheng, Chutasombut, Tapee, Totob, Hatta, Jannak, Jomoei, Inkaew, Yamroi, Mongkolchaisit, Sampipat, Choodam, Bupheng, Paluang, Niamrat, Hemphan, Saengjan, Chaiwong, Sempipat, and Rattanarangsi