'ด้วย (dûai)' in Thai language is used to imply that along with the action stated in the main clause, the subject or object is also doing another action or is in another state. Providing additional information, it functions similarly to the english words 'also', 'too', or 'as well'. It is versatile and can be used with different verbs and phrases to express additional action or state. 'ด้วย (dûai)' is typically placed after the verb or at the end of the sentence.