Tax likely at vesting  for RS, tax at vesting for RSU. Taxable amount is fair market value of the shares on the tax event. 

Expatriate employees ceasing employment or leaving Singapore may be deemed to have vested in RS/RSUs and be subject to taxation upon termination/leaving Singapore.

No tax on sale.

Allowed if treasury shares used to settle awards and subsidiary reimburses parent under a written agreement, but limited to the amount that the parent paid to acquire the treasury shares minus any amount paid for the shares by the employee.

Income Tax:
Generally, no withholding (except for certain expatriates ceasing employment and/or leaving Singapore based on deemed equity income).

Reporting requirements apply.

Social Insurance Contributions:
Generally, no.

Generally, employee share plan exemption applies.

Certain subsidiary director reporting obligations apply.

None.

Plan and agreements should indicate plan is discretionary.

Written consent from employees for the transfer of data abroad is recommended.