Tired of buying stocks based on others' tips and then losing money without knowing why? I encountered this situation so often that I decided to study ROA carefully because it’s a tool that shows whether management is truly effective or just letting money sit idle.

ROA (Return on Assets) simply measures how well a company uses its assets to generate profit. The formula is straightforward: (Net Profit / Total Assets) x 100 to get a percentage. It indicates how many baht of profit a company can generate from every 100 baht of assets.

A clear example illustrates this well: Coffee Shop A invests heavily—expensive building in a prime location, costly coffee machines, assets worth 10 million baht, but only earns 500,000 baht profit this year = ROA of just 5%. Meanwhile, Shop B rents a small space, assets worth 1 million baht, but makes 200,000 baht profit = ROA of 20%. Looking only at the bottom-line profit, Shop A seems wealthier, but if asked who manages smarter, it’s obvious that Shop B wins hands down.

Now, what should ROA be to consider it good? Generally, over 5% is acceptable, passing the threshold. Over 10% is considered excellent. But industry matters too—power plants or airlines (asset-heavy industries) with ROA of 5-7% are already impressive. For software companies (asset-light), if ROA is below 10%, it indicates poor management.

The key is to compare ROA with competitors in the same industry. Never compare a bank’s ROA with a tech company! I’ve seen many confuse ROA with ROE because ROE can be manipulated with high leverage, but ROA cannot be fooled. If a company borrows to inflate figures, ROA still reflects the true picture.

When scanning stocks, look at three things: first, high and consistently rising ROA = top efficiency. Such companies have a strong “Economic Moat” and are good to hold and sleep well. Second, ROA that’s steadily growing = a sign of a big rally. For example, from 5% to 7%, then 9%, this is a good moment to catch before the market realizes. Third, low or declining ROA = avoid because it indicates failed investments.

Compare Apple and Tesla as examples: Apple achieves 25-30% ROA because design is done in the US and manufacturing in Asia, avoiding large factories. Tesla, on the other hand, does 5-15% because it builds massive factories worldwide. When the EV market price war from China hits, Tesla has to accept lower profits, and ROA drops. This is the natural cycle of asset-heavy businesses that must be understood.

Limitations to know: don’t use ROA to evaluate banks because their balance sheets are unusual. Bank ROA is often just 1-2%, but that doesn’t mean they’re bad—it's just their business model. Also, beware of accounting tricks—skilled accountants can temporarily make ROA look better than reality.

In summary, ROA should be industry-specific. The key is to look at trends and compare with competitors. If you find a stock with high ROA, increasing over time, and better than peers, that’s a stock worth following. No need to randomly follow tips from others anymore.