Why does my recording of the tone 'mai ek' sound wrong to native ears?

I’ve been recording myself practicing minimal pairs in Lao, but my partner says my 'mai ek' (low tone) sounds more like a flat mid-tone. I’m struggling with the physical tension required for the glottal check on short vowels. Does anyone have specific tips for adjusting vocal cord tension to distinguish these tones in Lao, or should I shift my focus to listening exercises first?