It's challenging to guarantee a "high salary" immediately after the 12th grade without further education or specialized training, especially at the age of 18. Most high-paying jobs typically require a degree or significant experience. However, some options can provide a decent starting salary and opportunities for growth with time and skill development. Keep in mind that "high salary" is subjective and can vary based on location, industry, and individual skills.

Here are a few avenues you might explore:

1. Government Jobs: Several government organizations offer entry-level positions for 12th-pass candidates. These jobs often provide job security and benefits, although the initial salaries might not be exceptionally high. Some examples include:

• Staff Selection Commission (SSC) Exams: SSC conducts exams like CHSL (Combined Higher Secondary Level) for posts such as Lower Divisional Clerk (LDC), Data Entry Operator (DEO), and Postal Assistant/Sorting Assistant.
  
  
• Railway Recruitment Board (RRB) Exams: RRB conducts exams for various non-technical and technical roles.
  
  
• Defense Services: You can explore opportunities in the Army, Navy, and Air Force as a soldier, airman, or sailor. Exams like NDA (National Defence Academy) for officer-level roles require further training.
• Police Constable: State police departments often recruit constables based on 12th pass qualifications.

2. Merchant Navy: If you are willing to undergo pre-sea training, a career in the merchant navy can offer a relatively good salary and opportunities for travel. Various roles are available after completing the required certifications.

3. Technical Roles: Depending on your aptitude and any vocational training you might have, some technical jobs might be available:

• Data Entry Operator: Requires good typing speed and accuracy.
  
  
• Technician Roles: In some industries, basic technician roles might be available after the 12th, with on-the-job training.

4. Sales and Marketing: Entry-level sales and marketing roles might be available, where your earning potential can increase with performance-based incentives.

5. Call Center/BPO: While not typically considered high-salary, some Business Process Outsourcing (BPO) or call center jobs might offer a starting salary that is decent for an 18-year-old without a degree.