Just look what happened a few years when a previous Alpha-S person stood firm. He was, despite being a
PR ( Permanent Resident ) booted out of SQ and Singapore.
As Ark Pilot rightly points out there is no "standing firm". You will get what SQ decide and if you want to say no then like some time ago it 2.5 years to agree a new CA and after the Ministry get involved to settle dispute if Alpha-S still do not agree then standby to be threatened with no back pay which quickly sorted it out last time around.
This is still a good job for some depending on your own personal situation. Personally I would not have left my company to join SQ based on current rental costs in Singapore,and currency exchange rates.
Although the Bond is large you do at least get it all back after 5 years on the line. Just make sure you are prepared to stay the course and know what you are letting yourself in for and do not rely on large bonuses year on as the formula could change and goal posts moved.