Articulatory adjustments are often necessary to ensure that closure voicing will be present in stops (Rothenberg 1968). One common adjustment is to enlarge the supralaryngeal cavity volume via tongue root advancement (Westbury 1983). This study uses ultrasound to examine tongue positioning during Brazilian Portuguese and Thai stops. Portuguese has a two-way laryngeal contrast: voiced and voiceless (unaspirated), and Thai has a three-way contrast: voiced, voiceless unaspirated, and voiceless aspirated. Eight native speakers of each language recorded phrase-initial stops followed by /a/. Results show a clear distinction in tongue position between voiced and voiceless unaspirated stops in both languages. Tongue root is more advanced for voiced compared to voiceless unaspirated in alveolar and velar stops. For labial stops, Thai speakers lower the tongue front (which is another cavity enlargement maneuver) whereas Portuguese speakers advance their tongue root for voiced stops. The results suggest that speakers of both languages employ tongue positioning for voicing during closure. How the tongue position is operationalized may be language-specific as long as voiced stops have a larger cavity volume. On the other hand, the role of tongue position for aspiration is less clear since in Thai, alveolar stops and velar stops show the opposite pattern when voiceless unaspirated and aspirated stops are compared.