It is certainly permissible to use sources which are not in the language of the essay, but translation into the target language is required, one cannot assume that the reader understands the original language.

For the Bibliography/Works cited, my preference would be to list the source in its original Thai version, but with the English in brackets, to help the reader.

Your bibliography will have the entries in Thai characters first in the document. Any in-text citation to Thai sources will be in (Thai characters [English translation]).

Ex:

Citation in Thai [English translation]

Works Cited Example:

วงษ์ปัญญา, ธนกร [Wongpunya, Thanakorn]. “โรงงานยาสูบรวยแค่ไหน และเอาเงินไปทำอะไรบ้าง.”  [How rich is the Thailand Tobacco Monopoly and where does the money go?] (candidate translation). The Standard, The Standard, 30 Aug. 2018, thestandard.co/thailand-tobacco-monopoly/.