Kaempferia Parviflora (Thai Ginseng) is a herb that has some historical and medicinal usage for treating metabolic ailments and improving vitality in Thailand and limited to surrounding regions. It is also reported to be an aphrodisiac compound and physical enhancer.
Currently, the research on Thai Ginseng is at a moderate level and starting to get human trials. It appears to be 'healthy' and a good source of a class of bioflavonoid compounds with methoxy groups added to them, known as methoxyflavones.
That being said, the research on its aphrodisiac effects in mice indicate that low doses are weak to moderate in potency and higher doses fail to exert any aphrodisiac effect. It does not appear to increase testosterone in otherwise normal rats (although it may in castrated rats), and although it appears to have a variety of mechanisms to be pro-erectile, these have not been tested for potency in a living system. The mechanism of pro-erectility is fairly unique and interesting, but the one study to investigate whether or not it could inhibit PDE5 (one of the mechanisms of Viagra) failed to establish whether it was selective. Selective PDE5 inhibitors are good pro-erectiles without many side-effects, but the non-selectivity (currently not established) may lead to gastrointestinal side effects.
At least one study has noted that it can increase functionality and cardiovascular performance in otherwise healthy persons over 60, but an acute study in youth failed to find any performance enhancing effects at 1.35g (recommended dose, or at least near it).
Currently, Thai Ginseng seems to be weakly promising on proerectility with the other claims not really being better than other possible supplement choices.