Can paying off a payday loan help improve my credit record?

Much depends on the type of loan you have borrowed. Illegal payday loans are usually not listed on your credit report. Needless to say, they are less likely to hurt your FICO score. Legal payday loans are listed on your credit report. When you make timely payments on them, your FICO score improves gradually.

Yes, if you repay legal pdls, it can improve your credit score if you do not have much negative items in your report. In case of illegal pdls, you just have to pay the principal amount. It is not reported as a defaulted loan in your credit report.
It is better to check your credit reports periodically.

Legal payday loans are listed in your credit report. If you have any legal payday loans, pay them off and your credit score will improve.

Yes. illegal payday loans will not be listed in your credit report. However, repay the loans can't give you an excellent credit score. To boost your score, you have to manage your bills properly. You need to stay within your credit. Also, you should add motive information on your credit report to build a good credit score.