Aims and objectives/purpose/research questions: We investigate semantic interaction in bilinguals' topological relations descriptions in a small-scale, non-standardized, egalitarian, long-term multilingual setting in Malaysia. Design/methodology/approach: Two groups of bilingual speakers of Jedek and Jahai (8 Jedek-identifying, 6 Jahai-identifying bilinguals) and two groups of monolingual Jedek and Jahai speakers (15 Jedek, 3 Jahai speakers) described the Topological Relations Picture Series in a director-matcher task, the bilinguals completing the task in both Jedek and Jahai. Data and analysis: We compare the semantic boundaries of Jedek and Jahai topological relation markers (TRMs) as used by the monolingual and bilingual groups in extension maps and congruence analyses. The analyses focus on the TRM klɛŋ, which is identical in form but semantically different in the two varieties. Findings/conclusions: We find evidence for asymmetric interaction in the expression of topological relations in Jedek and Jahai, with bidirectional influences in the Jahai-identifying bilinguals and a unidirectional influence of Jedek on Jahai in the Jedek-identifying bilinguals. This is commensurate with predictions based on Muysken's framework of bilingual optimization strategies. Originality: The analyses shed new light on the nature of semantic interaction in bilingual systems by providing evidence from hitherto understudied bilingual language production in small-scale, non-standardized, egalitarian settings. Significance/implications: The results suggest that Muysken's model is useful for understanding different bilingual outcomes, and highlight the complexity and connectedness of bilingual semantic systems. They also stress the need for more work in a variety of bilingual settings if we are to more fully understand the nature of bilingual systems. [ABSTRACT FROM AUTHOR]