This study investigated the effects of linear distance, agreement attraction, and working memory (WM) on the processing of English third-person singular subject-verb agreement by second language (L2) learners whose first language (L1) is Thai. Grounded in the Linear Distance Hypothesis (Gibson, 1998, 2000), the study hypothesized that linear distance, agreement attraction, and WM would affect L1 Thai/L2 English learners' processing of the agreement in question. Thirty Thai-speaking nonnative speakers (NNSs) with advanced L2 proficiency and 30 native speakers (NSs) were included. A word-by-word self-paced reading task was employed to determine the three effects. The results revealed longer reading times (RTs) in the long-distance context (e.g., 'The leaders in the cars meet on a monthly basis.') compared to the short-distance counterpart (e.g., 'The waiter lives in a small town.') in the critical region, i.e., the verb, for both the NNSs and the NSs. The agreement attraction effect was not observed in either the NS or the NNS data as similar RTs were obtained between the matched (e.g., 'The teen on the ladder works on her summer break.') and mismatched (e.g., '*The lawyers on the ship travels from city to city.') conditions. This was speculated to be due to the mismatch asymmetry effect (Barker & Nicol, 2000). WM and its interaction effects with linear distance and agreement attraction were partially observed as the low WM group exhibited shorter RTs in the ungrammatical-mismatched compared to the high WM counterpart. The effect of WM was assumed to be moderated by the NNSs' high proficiency.