It can't be done - unfortunately
I had the same problem and chanced upon this post.
I contacted paypal and this was their reply - in short, it can't be done if you're based in Singapore.
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We appreciate your interest in using your PayPal account to receive donations. Of the 190 countries and regions where we are available.
To offer certain services in various countries or regions, we must be fully compliant with local and international financial laws to avoid difficulties in the future with our services. We made the decision not to offer this service because of financial regulations and the needs of our business.
You may accept payments for goods or services for your charity but you can’t receive direct donations using PayPal.
We understand how this may be inconvenient for you, and we appreciate your understanding.
It is my pleasure to assist you. Thank you for choosing PayPal. Your satisfaction is important to us. We welcome your feedback and hope you recommend us to your friends and family.
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