I am 40 years old with 135K SGD crypto assets (diversified), 85K SGD precious metals (physical), 13K SGD US/CN tech stocks and 11.5K SGD REITs. What rebalancing should I do?

It seems like you are either very averse to counter party risk, or you are preparing to flee the country.

It depends on what's your end goal.

If you have a goal and a number you're working towards.

Ask yourself which of this asset class is not helping you to reach your goals.

If so, are you able to channel this low performing funds to meet this goals?

If after rebalancing, are you ok if downturn happens and you have to hold it for 3-5 years?

If you're okay, go ahead and concentrate it.

If not, just be diversified.