Can you tell me how to fix spider veins on my thighs?

Vein evaluation. If you have a few spider veins then sclerotherapy would be the treatment of choice. If you have many spider veins then you should consider having a venous evaluation with a venous reflux ultrasound to see if you have underlying reflux (leaking vein valves) which may be the cause of the spiders. A vein specialist would be able to evaluate you.
Sclerotherapy Best. Spider veins on the leg are best treated by sclerotherapy. Most vein specialists will treat leg spider veins with sclerotherapy because it not only treats the tiny spider veins but the slightly larger and slightly deeper veins that feed the spider veins. Lasers cannot treat the feeder veins and so cannot completely treat the problem, but for the smallest reddish veins they can be effective.