This study compares how the native speakers of Thai (TTs) and American (AEs) as well as the Thai learners of English as a foreign language with high exposure to English (TEHs) and those with the low exposure (TELs) perform the speech acts of compliments (Cs) by taking the context of age into their consideration. The data were collected by means of a written discourse completion task (WDCT). The analysis of the data examined the pragmatic structures and in particular, strategies of Cs. The six pragmatic structures in terms of head acts [H] and supportive moves (S) were found. They were [H] only, [H]+(S), [H]+(S)+[H], (S)+[H], (S)+[H]+(S), and (S) only. Surprisingly, as opposed to other speech act studies, the AEs showed their preferences towards (S)-oriented structures while the TELs tended to favour [H]-oriented structures in giving Cs in all given situations in the context of age. A closer look at the C strategies exhibited cultural specific preferences among the AEs and the TTs which explain the interlanguage phenomena among the TEHs and the TELs. The interlanguage phenomena found in the two groups of learners may be seen as their incomplete mastery of English but they also could be interpreted as the communication strategies of the TEHs and the TELs to smooth their interactions in English. [Contains an English Written Discourse Completion Task (WDCT in English), and a Thai Written Discourse Completion Task translated version of English WDCT into Thai.]