Can I ask the seller to pay my closing costs?
Yes. You can request a seller credit (seller concession) toward closing costs in your offer, within your loan program's limits. It is more likely to be accepted when the home has been on the market a while. ListingCraft for Buyers lets you put your terms in an offer package to the listing agent.
A credit lowers your cash to close but not the price, and some buyers offer a slightly higher price to cover it. The appraisal still has to support the price.