What is the ruling of Islamic law concerning a married man who is compelled to travel frequently due to work, leaving his wife to care for the children, and he is unable to control himself during travel and fears falling into sin?

If you are able to marry another woman who can accompany you on your journey, then do so and be just between your two wives. However, if you are unable to do that, or unable to bring your wife with you, then return to your country. The well-being of one's faith and avoiding temptation are great benefits. If you cannot return due to your urgent need to travel, then fear Allah, be patient, and strive for chastity. You should fast while guarding your hearing and sight. Seek help and hold fast to Allah. Occupy your time with what benefits you, be keen on the company of the righteous, and make abundant supplications.