Hi.
The japanese army had three types of flamethrowers avaliable in 1941:
Type 93:
Type 93 large:
Type 100:
Type 93 and type 100 were also mounted in weapon ports of the armoured engineer vehicle SS. This vehicle could be equipped with a large flame oil tank in the back and in one version also several tanks between the suspension parts
In late 1941 the type 100 flame thrower hasn´t replaced the type 93 in all units so based on the informations avaliable to me it is impossible to say exactly which one were used at Hong Kong.
Yours
tom!