How do you usually plan for retirement if you want to travel a lot later?

How much is a lot. I think first, it helps to dimension how much that costs, and then work a savings/investment plan to cover those expenses.

Travelling need not be expensive, in fact can be cheaper than similar lifestyle in Singapore. Go to places where is much cheaper, having deflation like Chinese cities, South East Asia, Eastern Europe or even further.

Will get some dividend stocks for passive income to fund the travels

Travel alot to where? Do you mean travel all around the world? Even to Artic Antartica? Is that what you want? You can spend a long time traveling within US, Europe, China itself. If travel within Asia, its even cheaper. Once you set a realistic target, then you can plan.