Aren't you waiting on SIA's reply after your first interview?
Taking lessons in Seletar is really expensive. Even before your first lesson, you'd have to put down a hefty deposit, plus some misc fees, amounting to a few thousand dollars. If you want that PPL, it'll be much cheaper in M'sia. IIRC, a PPL in M'sia will cost about S$8000, while in s'pore, the PPL will cost more than twice as much. Moreover, in s'pore, you'd have to be content with a tiny and crowded training area.
If you just want something to impress the interviewers with, a good alternative would be to simply go for a familiarisation flight with the flying club. It will cost you about S$400 for an hour's flight inclusive of other fees like a day pass, instructor fees etc.
If you're still keen on taking your PPL in s'pore, then I'd say go for it, even if SIA takes you in before you actually complete the course. The extra hours would certainly help you, and such an investment will never go to waste.