1. in this matter only an allotment letter is issued
2. there is no agreement also which has been registered in joint names
3. if your wife is willing to pay you half of what is already paid to the builder, then a simple agreement can be made between you and your wife recording this arrangement and transaction
4. this agreement can be made in Singapore itself and signed before the notary public there
5. you can then send the notarised agreement to the builder by courier
6. the formal registration will then be done only with your wife and you will be out of the scene
7. as regards the bank too there wont be any issue since the loan is not yet disbursed
8. i am assuming that the bank loan application was made jointly by you and your wife. So in that case, you can submit the same agreement to the bank as well so that it can remove your name from the loan application and process the loan only in the sole name of your wife
9. the agreement as above can be signed in triplicate, each being an original. One original can be retained by your wife [since she is paying you and you can have a true copy of the document for your record] and the other 2 originals can go to the builder and bank
10. while the agreement is in transit for being delivered to the builder/bank, you can notify both about the said agreement by email and also inform that the hard copy of the agreement will reach them in due course by courier