The pendoko is classic Terengganu style. The buntut style is also Northern Malay Peninsula. The hilt form is also in classic Terengganu style, not at all uncommon. I would say the keris is not likely assembled in Singapore, but in Northern Malay Peninsula where all the craftsmen for these parts reside.
The main sheath is really unusual, so is the horn fitting at the mouth, so I have no comments for that.
The blade does look N. Malay Peninsula (in fact, Terengganu) to me. So does the pamor. There are a number of N. Malay Peninsula blades with such pamor. In fact, it is one of the few pamor types found on N. Malay Peninsula blades. Perhaps there was a transfer of technique/technology at some point in time from Madura/elsewhere to N. Malay Peninsula. If this blade were to be presented to keris collectors in the N. Malay Peninsula, I don't think it would be identified as an unusual keris.
But of course, we can never be sure if such kerises were made elsewhere and exported to N. Malay Peninsula. After all, people move, trade moves.
I think the sharing of opinions is good and provides fresh perspective to examine things we see commonly and have come to accept without questioning.