I recall that up to 1980, the only Indian in a bank in Singapore is either an office boy or messenger. All the locals banks would only hire chinese-ed front line staff and all the International Banks such HSBC, SCB etc would hire english ed and many were Eurasian front line staff.
POSB was a refreshing exception. Truly Singaporeans and in the 90s, they went all out to get local Chio Bu with multicultural tilt. Feeling guilty the local banks began to hire Malays and Indians as front line. DBS like always stood in between.
Even until the 2000, no local chinese bank would hire a non chinese as fresh grad hire. OUB made an exception when they had a VP in 1998 who was an Indian.
Interestingly any boycott will work in the favour of international banks who prefer that the lower end not bank with them. Higher end will require online TT service which none of the locals do. Furthermore, they compete in different space. Look at DBS, they gave out the least compensation after the minibond debacle. Look at the International banks in Singapore.