I'm not an attorney but possession of a product designed to produce an effect substantially similiar to synthetic THC appears to be a felony.
H&SC 481.106 Classification of Controlled Substance Analogue
For the purposes of the prosecution of an offense under this
subchapter involving the manufacture, delivery, or possession
of a controlled substance, Penalty Groups 1, 1-A, and 2 include a
controlled substance analogue that:
(1) [... has a similar chemical structure...] ; or
(2) is specifically designed to produce an effect substantially
similar to, or greater than, a controlled substance
listed in the applicable penalty group.
Synthetic THC is listed in penalty group 2:
Tetrahydrocannabinols, other than marihuana,
and synthetic equivalents of the substances contained in
the plant, or in the resinous extractives of Cannabis, or
synthetic substances, derivatives, and their isomers with
similar chemical structure and pharmacological activity such as:
delta-1 cis or trans tetrahydrocannabinol, and their optical
isomers;
delta-6 cis or trans tetrahydrocannabinol, and their optical
isomers;
delta-3, 4 cis or tetrahydrocannabinol, and its optical
isomers;
compounds of these structures, regardless of numerical
designation of atomic positions, since nomenclature
of these substances is not internationally standardized;