How do I get my son to stop spending so much money on branded goods?

Reduce his budget, and ask a friend or relative to talk to him.

my own experience says that mother/father talks to kids are a bit less "worthy" than a trusted relative, or a trusted friend that the kid loves.

And most of the time, kids go for brandeds because of peer pressure. observe his friends and see if he is indeed trying to cope with peer pressure

Hey there! Is he spending his own money, or is it your money? If it's the latter, I think you can control him. Limit his spending by giving him a debit card with a fixed amount every month. If it's the former, a little tricky but I think what works is to show him alternatives on what the $ spent on material goods can be used on for a greater purpose in future.

Do take the time to communicate with your son, understand his daily life and circle of friends!

Show him examples of people who do well and achieve much without those stuff.

Send the message that it is a good to have but its not a must have, a want, not a need.

Tell him that many rich are humble people and that he does not need to wear branded goods to show that he has money. It is ultimately, superficial.

I Guess we all have our own perspective and methods (sort of) , the key is to Ensure that he understand the behind the scenes of such big Brands.

In addition, it’s always worth while to spend some time with the less privileged and fortunate. You do not need to go far where ever you lived in SG, there are Hawker centres across the island. Have a meal and explain to him the hours time effort of our Hawkers and the cost.