Yes. A person wishing to buy a land, including a foreigner, may purchase a land without being present at the time of registration of ownership at the Land Department. This shall be done by appointing, by a power of attorney, a lawyer to act on your behalf.
Nevertheless, if you are married to a Thai, you, as a foreign spouse of a Thai, is required to declare in a written agreement that a fund, of a purchase of land, is purely of your Thai spouse as her personal affair before marriage. This procedure may be done by signing such declaration abroad, and demand for a certification at the Consulate of Thailand in your country.