* Q1 loss smaller than expected

* Sales and marketing spend increases 9 pct

* Shares fall 5 pct in extended trading after Q2 forecast (Adds share fall in first paragraph)

By Arjun Panchadar

May 30 (Reuters) - Cloud storage provider Box Inc's shares fell about 5 percent in extended trade on Wednesday, after the company issued a conservative second-quarter forecast.

Box, whose shares have risen nearly 45 percent in the last 12 months, also reported first-quarter revenue that edged past Wall Street estimates amid a ramp-up in spending to attract paying customers.

"I think investors are always ... looking for us to continue to raise guidance ... We think that makes sense but obviously we want to guide to numbers we feel very comfortable and confident," Chief Executive Officer Aaron Levie told Reuters.

Box forecast second-quarter revenue at between $146 million and $147 million. Analysts on average were expecting $146.1 million, according to Thomson Reuters I/B/E/S.

The company also said it has been investing in cyber security, compliance and administrative technology and plans to add more sales personnel as it expands in markets such as Germany, Australia and Canada.

"The growth rates of those markets are still lower because of how early we are building out our presence ... But we do expect they will be able to increase in the near future," Levie said.

Box, which competes with Dropbox Inc, Microsoft Corp's OneDrive and Google's Drive, said its revenue rose 20 percent to $140.5 million in the quarter ended April 30.

Dropbox beat expectations for quarterly results and topped estimates for paying subscribers in its first financial report as a publicly traded company earlier this month.

Box signed 85,000 paying customers in the first quarter, up from 82,000 in the fourth quarter, but also spent 9 percent more from last year to attract them.

Net loss attributable to Box's shareholders narrowed to $36.6 million, or 26 cents per share, from $40.1 million, or 30 cents per share.

Excluding items, the Redwood City, California-based company lost 7 cents per share.

Analysts had expected revenue of $139.7 million and a loss of 8 cents per share. (Reporting by Arjun Panchadar in Bengaluru; Editing by Maju Samuel)