Yes, as a Singapore citizen with a husband who is a long-term pass holder, you can purchase an HDB flat under the Non-resident spouse scheme. If you are at least 21 years old, your husband must have a valid Long Term Visit Pass or Work Pass of at least 6 months from the date of issue at the point of your HFE letter and resale flat application. If you are 35 years or older, the pass can be of any validity period.
For new flats, you are only eligible to apply for 2-room BTO Flexi units in non-mature estates.
Best of luck with your flat purchase!